System for sintering



Nov. 12, 1946. w. F. JOHNSON SYSTEM FOR SINTERING Filed May 13, 1943 IVENTOR. Val/a]? fofimmn/ atented ov. 12, 1946 SYSTEM FOR SINTERING Walter F. Johnson, Berkeley, Calif., assignor to American Smelting and Refining Company, New York, N. Y., a corporation of New Jersey Application May 13, 1943, Serial No. 486,798

6 Claims. 1

This invention relates to metallurgical operations and more particularly to a system for automatically controlling the operation of sintering machines.

In the process of roasting ores on a sintering machine, and especially sulphide ores, it frequently is highly desirable to recover the S02 evolved in the reaction between the oxygen of the combustion supporting air and the sulphur of the ore. For reasons known in the art, it is advantageous to produce a gas from the roasting or sintering operation which is uniform with respect to volume and S02 concentration in addition to producing a uniformly sintered product. This is particularly so when the S02 containing gas is to be used for the production of sulphuric acid or other products of sulphur dioxide.

Heretofore the control of the operation of the machine has been left largely to the manual skill of the operator who, among other things, may be charged with the duty of controlling the speed of the machine as well as other factors by a system of rather hit or miss tests and observations from which he manually changes the controls ,from time to time in his efforts to produce the The invention is hereinafter more fully described in connection with the operation of that type of sintering machine which has come to be known in the art as a Dwight-Lloyd straight line machine but it will be apparent as the description proceeds that the invention will lend itself to other sintering machines.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, asto its objects and advantages, and the manner in which it may be carried out, may be better understood by referring to the following description taken in con nection with the accompanying drawing forming a part thereof in which Fig. 1 is a view in elevation, partly in cross-section and partly diagrammatic, of a sintering machine of the Dwight- Lloyd type embodying the system of the invention, and Fig. 2 is a cross section taken on the line 2-2 of Fig. 1.

Referring to the drawing, there is shown a sintering machine of the straight-line type havthe charge.

ing the usual structural frame members, I, ll, l2, cars l3 provided with wheels i4 riding on suitable tracks IS in the upper part of the machine and tracks iii in the lower part. The cars or pallets l3 are engaged by the rotatable bullwheel I! at the feed end .of the machine which causes them to be pushed in the direction of arrow l8 on tracks i5 where they are turned over and dumped at the discharge end. The pallets then travel upside down along the inclined trackways Hi again to be engaged by the bullwheel to continue their cyclic travel.

Mounted above the path of travel of the pallets at the feed end is a charge hopper or chute l9. Material to be sintered is fed into the hopper l9 by a turntable 20 on to which the material is charged from a .bin 2i. A suitable plow or scraper indicated at 22 deflects a'predetermined amount of material from the surface of I A will be augmented with such combustible as may be necessary to insure sufflcient heat for sintering in the event the sulphides in the ore are deficient.

As the pallets pass under the discharge end 23 of the chute i9 they are supplied with an adiusted amount of material to be sintered, called An adjustable back plate 24 may be used to level off the surface of the charge in the pallets Ill. The charge is then given an initial ignition by means of a flame muflle or igniter 25 after which the pallets pass over a windbox and under a hood designated generally by reference numbers 26 and 27, respectively.

In this machine the windbox is interiorly divided by a, partition member 28 provided with a baille 29 to provide in effect a first windbox 30 and a second windbox 3! which preferably are of unequal size, the first being larger. The hood 2! surrounding the discharge end of the machine extends over the top of the machine and completely covers the second windbox 3| and all but a small portion of the first .windbox. The sides of the hood extend downwardly around the tracks and engage the windboxes in a manner to provide a substantially air-tight hood having an opening 32 through which atmospheric air is drawn into the hood chamber 83. Extending from the end of the hood 2'! nearest the igniter 25-for a substantial distance over the first windbox 30 is an inner hood 84. There is a seal between the windbox and the pallets and the machine is provided with a dead plate beyond the windbox as is known in machines of this type.

The second windbox is provided with a circulating pipe 35 which leads from the second windbox 3l to a suction blower or fan 36 and thence into a pipe 38 which opens into the hood chamber 21 over the first wind box 30. A discharge pipe 40 interconnects windbox 30 with flue 4i via suction blower or fan 42.

In operating a machine of this type in conventional manner, air for the sintering operation is drawn through the opening 32 through the hood chamber and down through the sulphide charge on the pallets into second windbox 3| by fan 36, the gases from the second windbox passing therefrom through circulating pipe 35 thence through circulating pipe 38 and thence into the main hood above the first windbox. A bailie 3.5a in the hood 21 prevents the air drawn into the machine at the discharge end from fiowing freely and directly over the charge above the first windbox 30.

By providing for recirculation of the gases a higher concentration of S02 in the gas ultimately discharged from the machine is obtained than otherwise. However, due to variable factors entering into the sintering operation, it is dimcult, and sometimes impossible, to obtain a uniformly sintered product and a uniform volume of SO: gases of uniform, relatively high concentration.

One very important factor in obtaining uniformity is controlling the speed of travel of the pallets so that the charge will be burned through to the grate bars of the pallets when the pallets have passed over the last windbox. It has not been uncommon practice for the workmen to dig into the charg with a bar before it is discharged from the machine to see if the product is sintered satisfactorily and then by hand adjust the mechanism which controls the rate of travel of the pallets. Because the charge may vary, the rate of sintering also may vary. pallets and believe the charge burned out too much; so, he would speed up the machine to overcome this, only to find the next pallets moving along might not warrant the extra speed.

In. accordance with the invention, these undesirable drawbacks are eliminated by providing a controller responsive to the amount of air passing through the charge and suitable mechanism operatively connected whereby the speed of the pallets will automatically be adjusted to produce uniform sintering. At the same time, the volume of combustion gases produced may be kept substantially constant, with a relatively high concentration of 802.

When the charge passes under the igniter, it is given an initial ignition and the combustible material burns, thus eliminating the volatile substances and driving off the water.- As this progresses, as the pallets travel over the windbox, the charge becomes progressively more porous and more air is pulled through, consequently the porosity largely determines the amount of air pulled through and therefore the rate of burning of the combustible in the charge. Hence, under usual conditions of operation in order to obtain uniformity of sinter, the speed of the machine should increase automatically when the volume of air passing through the charge increases beyond a predetermined amount, and the speed should automatically decrease when the volume decreases. Thus, the volume of air passing through the charge may be maintained substantially constant by regulating the speed to take careof such variations so that the charge will be burned to the grate bars by the time the pallets reach the end of the last windbox.

The amount of air entering the hood and passing through the charge'bears a proportional relationship to the draft or suction in the hood. To take advantage of this condition to automatically control the operation of the machine there is provided a conduit 44 which connects the interior of the hood chamber 33a above the first windbox with a controller (designated generally by reference character 50) which will An operator might dig into one or two arious forms.

operate a speed reducer mechaism 5| in response to changes in pressure (suction) within the hood; the speed reducer being driven by a suitable prime mover 52 by a belt 53.

The controller is shown more or less diagrammatically and its mechanism per se may be of Such an instrument, now offered for sale under the trade name Bristol, may be used for the purpose.

As shown, the conduit 44 is connected to a recorder or indicator type of draft measuring instrument 54. The controller instrument designated :i i has an arrangement or controlling device vhich is operative, at a predetermined draft setting, to open a small valve when the draft exceeds the setting, to allow air under pressure to pass through conduit 55 which is connected to a suitable source of compressed air (not shown). The valve arrangement is such that the air pressure may thus be caused to flow into conduit 58 when the draft exceeds a predetermined setting and to flow out of conduit 56 when the draft falls below a predetermined amount. Conduit 56 is connected to the interior of a bellows 51 which is contractible and expansible in response to the air pressure therein. The bellows 51 which is carried on a suitably mounted bracket 58 also mounts a rod 59 slidable in an aperture in the bracket. The outer end of the rod is linked to a lever 60 as by a pin 6|. The lever is pivoted to the bracket at one end providing a fulcrum 62. The other end of the lever is attached to a rack 63 by means of a pin 64' slidable in a slot 65' in the lever.

The rack 63 meshes with a pinion 84 fixed to a shaft which is a part of the variable speed reducer 5|. A rotation of pinion 84 will cause a contraction or spreading of conventional coneshaped driving pulleys fixed to shaft 65 in known manner and thus control the linear speed of driving belt 61 which in turn rotates the bull wheel I! through pulleys 68 and 8B and a train of gears 68, 10, ll. Shaft 65 is driven, as indicated, by the drive shaft 12 to which is fixed pulley 73 driven by belt 53. Also driven by the speed reducer is a belt I4 which rotates turntable 20 on its axis through a set of bevel gears and shafts,"l5, 18. ll, 18, 19 and 80. Hence, it will be observed that the speed of rotation of the turntable 20 is correlated with the speed of the bull wheel II. A speed indicator 8| connected by a belt 82 to the speed control shaft 85 currently indicates the speed of travel of the pallets, the hand 83 being movable over a graduated dial 44.

In the operation of the machine, the rate of feeding the charge from the turntable through the chute I9 is adjusted and also the speed of the pallets is regulated in accordance with the draft in chamber 33a over the first windbo'x ill to produce a desired amount of sintering when the sintered charge is dumped from the pallets at the end of discharge end of the machine. The controller device 50 is adjusted for these conditions and the setting to maintain the draft constant within narrow limits. The mechanism is such that if the draft increases in the chember 3311 over the first windbox the controller automatically operates the lever 60 when the draft exceeds the setting. This causes a corresponding movement of rack 63 to rotate pinion 65 and thus causes the speed reducer mechanism to speed up the rotations of the bull wheel and consequently the speed of travel of the pallets. This is desirable because an increased draft indicates too much burning before the pallets reach the end of the windbox. Speeding up the rate of travel compensates this so that the charge will be burned the. right amount just as the pallets leave the windbox 3 I. On'the other hand. if the draft decreases, that indicates not enough burning, as the porosity is insuiiicient to pass the While certain novel features of the invention have been shown and described and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes in the forms and details of the system of the invention illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. Apparatus for sintering ore which comprises, in combination, a driven variable speed reducer having a driving means and a means to change the driving speed of the said driving means; a sintering machine driven by said driving means,

said sintering machine having a substantially closed hood, a windbox and a blower mechanism to draw air into the hood chamber, through the charge and through the windbox of said machine;

and a controller mechanism connected to said chamber and to said speed reducer, said controller being operative in response to a change of pressure in said chamber to increase the speed of said driving means upon a predetermined increase in the draft in said chamber and to decrease the speed of said driving means upon a predetermined decrease in the draft in said chamber.

2. Apparatus for sintering ore which comprises, in combination, a driven variable speed reducer having a driving means and a means to change the driving speed of the said driving means; a rotary charger tumtable' to feed the charge to be vsintered driven by said driving means; a sintering machine driven by said driving means, said sintering'machine having a substantially closed hood,

a 3, Apparatus fbr sintering orescomprising: a

sintering machine 'having a train of pallets movable over a.windbox, means to cause said pallets to 'move in tandem over said windbox, a substantially enclosed hood over said windbox' forming a chamber, an igniter to ignite the charge on the pallets, and a blower to draw air into said chamber through an ignited charge on the pallets into said windbox to sinter the charge; a draft measuring instrument connected to said chamber; a controller mechanism connecting with said instrument and operative in response to a change in draft measured by said instrument; and a variable speed reducer mechanism connected to operate the pallet moving means, said speed reducer mechanism and controller mechanism being operatively connected with each other to change the driving speed of said speed re- :lucer mechanism in response to a change in draft in said chamber to automatically control the speed of travel of said pallets over the windbox in correlation with draft conditions in said chamber.

4. Apparatus for producing uniform sinter from ores amenable to sintering which corn-- prises a frame mounting upper and lower-trackways, a train of pellets movable on said track ways, a'wheel to move said pallets, means to charge said pallets at one end of the upper trackways, an igniter to ignite the charge in the pallets, a hood beyond the igniter forming a hood chamber over the pallets in their path of travel, a

windbox below said hood and beneath pallets travelling on said upper trackways, a blower connected to said windbox to draw air into said chamber, thence through the ignited charge into said windbox, a speed reducer r mechanism driven by a prime mover, said speed reducer mechanism being connected to rotate said wheel to move said pallets, a controller connected to said hood chamber and operative in response to a change of a condition in said chamber to cause.

said speed reducer to change its driving speed to change the speed of travel of said pallets under said hood.

5. Apparatus'for sintering ores comprising the combination with a sintering machine of the down-draft type defining a path of travel for,

the charge and having variable-speed driving means for conveying the charge along said path of travel, of means for measuring the draft at a selected point in the system, and controller means operative in response to significant changes in said draft to automatically actuate said driving means to increase the rate at which the charge is conveyed along said path of travel when the draft increases at said selected point and to de crease the rate at which the charge is conveyed along said path of travel when the draft decreases at said selected point.

6. Apparatus for uniformlysintering ore com- I prising the combination with a straight-line sintering machine of the Dwight-Lloyd type having pallets i for supporting the ore and driving means for moving the pallets through the machine, of -a draft-measuringlinstrument for measuring the draft under which the sintering I operation is conducted, and controller mechanism responsive to material deviations in said draft automatically effecting a compensating change in the speed of the pallet driving means.

' wan'mar'. JOHNSON. 

